Issue with Latest GDB on AIX with GCC-6.12

Pedro Alves
Wed Jan 25 14:01:00 GMT 2017

On 01/25/2017 01:52 PM, Pedro Alves wrote:
> On 01/25/2017 11:12 AM, Pedro Alves wrote:
>> On 01/25/2017 10:54 AM, Nitish Kumar Mishra wrote:
>>> Hi,
>>> The latest community gdb is not working with gcc 6.12, however, it
>>> works expectedly fine with GCC-4.8.5 on AIX platform.
>> What is gcc 6.12 ?
>>> #12 0x000000010007d994 in _ZL23gdb_rl_callback_handlerPc
>>> (rl=0x1100e92b0 "") at event-top.c:213
>> I only saw C++ frames up to here, and the exception should
>> be caught here.  I don't immediately see why that wouldn't
>> be working, though maybe it's the "noexcept"?  If you remove
>> that, does it fix it?  Maybe we need a level of indirection
>> here too, like in gdb_rl_callback_read_char_wrapper_noexcept
>> / gdb_rl_callback_read_char_wrapper.
> I could reproduce this on gcc119 on the compile farm (AIX 7.2),
> which has GCC 6.1.  I tried the workaround suggested above, but
> that didn't work.
> TBC, it's perfectly valid for a noexpect function to
> try/catch inside as long as no exception escapes out, but,
> compiler bugs are not unheard-of.
> I also tried replacing the TRY/CATCH macros with try/catch(...)
> thinking that it could be something with broken type info,
> and the runtime somehow not figuring out that that catch
> should really catch the exception.  Same thing, doesn't work
> for me.
> So I'm out of ideas.  It looks like a toolchain/runtime bug
> to me.

Sounds like a manifestation of:

 Bug 60939 - AIX: exceptions not caught when calling function via pointer

since ui->input_handler is a function pointer here:

static void
gdb_rl_callback_handler (char *rl) noexcept
  struct gdb_exception gdb_rl_expt = exception_none;
  struct ui *ui = current_ui;

      ui->input_handler (rl);
      gdb_rl_expt = ex;

> TBC, I'm not going to be looking at this further.  It's
> very uncomfortable for me to use that machine --- I get a
> bit too high latency, and emacs doesn't work.  I even tried
> to survive with vi, but then DEL/BS didn't work for me.  :-P

Pedro Alves

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